My wife and I just returned from a trip to Montana from PA during the recent hot spell in the midwest. Our 2011 Georgetown 350TS is equipped with a Generac Q65 generator that would quit running when the outside temperature would reach 100 degrees. When looking at the control board, it indicated "high oil temperature." After three days at the dealer, it still isn't known what is the problem. We are now considering changing out the generator to an Onan 5500, even at a substantial cost. Has anyone else had this problem with a Generac?

My wife and I just returned from a trip to Montana from PA during the recent hot spell in the midwest. Our 2011 Georgetown 350TS is equipped with a Generac Q65 generator that would quit running when the outside temperature would reach 100 degrees. When looking at the control board, it indicated "high oil temperature." After three days at the dealer, it still isn't known what is the problem. We are now considering changing out the generator to an Onan 5500, even at a substantial cost. Has anyone else had this problem with a Generac?

John Sirkoch
Renfrew PA
2011 Georgetown 350TS

I first have a few questions and if you feel your answers fit you can try the solution.

1. Do you have many hours of run time on the generator?
2. When you run it do you load up the generator or just have it run just lights and battery charger, etc?
3. Has the oil. filter been changed recently?
4. Open up the air filter and check filter if it is clogged or not. Clean

If you don't run generator often under full load the gas may have formed varnish in the carb. This may make it run lean which might make it run hotter than normal

Anyway I suggest to buy a spay can of carb cleaner
Open up the air filter and while the unit is running spray directly into the intake of the carb. You want to spray a lot and it may even stall out. That's OK. I would continue to spray for a few more seconds and then let the unit sit not running. If you have any varnish in the ventura or around the needle valve opening it will help to remove that old gas varnish buildup.
You can try this a few times and see what happens. It is a cheap idea to save you a lot more money in a new unit.

After awhile start and run it and turn everything you have on that you can that is 120 volts inside. I mean load that baby up and see if it overheats again and shuts down.

We had this issue a few years back on Class C's. At least for ours (and those were 4.0 models) the "oil cooler?" is installed woefully close to the exhaust. Grass or gravel lots everything seemed to be OK, but on asphalt it would just radiate too much heat and trip. They said the "thermostat" that triggers this was too low, so they put in a higher temp. At least that's what I recall from 4-5 years ago.

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We had this issue a few years back on Class C's. At least for ours (and those were 4.0 models) the "oil cooler?" is installed woefully close to the exhaust. Grass or gravel lots everything seemed to be OK, but on asphalt it would just radiate too much heat and trip. They said the "thermostat" that triggers this was too low, so they put in a higher temp. At least that's what I recall from 4-5 years ago.

I had this problem. The oil temperature sensor needed to be replaced. Its mounted on top of the oil filter housing. They do go bad and its easy to replace. Also, make sure you are running straight SAE30 oil as is recommended for temps over 40F I use a synthetic SAE 30 from Royal Purple. It's possible they used lower weight oil last time it was changed. You could also plumb in an oil cooler since there is not one on this model, but first try replacing the sensor, oil, and give it a good hose down.

I witnessed several gensets shutting down last week-end in 105 degree heat. To solve the problem most people were opening doors to the genset and running fans on them or finding shade of some sort to remedy the problem. I have a Honda 3000 and had to open the door to fix my problem after the heat reached 109. Air circulation is important.

I had this problem. The oil temperature sensor needed to be replaced. Its mounted on top of the oil filter housing. They do go bad and its easy to replace. Also, make sure you are running straight SAE30 oil as is recommended for temps over 40F I use a synthetic SAE 30 from Royal Purple. It's possible they used lower weight oil last time it was changed. You could also plumb in an oil cooler since there is not one on this model, but first try replacing the sensor, oil, and give it a good hose down.

Sounds like Ron has a great solution and probably the easiest place to begin solving the problem. Opening the door and placing a fan to blow at the generator might help to displace some of the heat as well but a more permanent fix would be my choice.

Not directly related to this thread but an interesting note: The Onan generators use positive ventilation from a fan mounted in a fan shroud under the engine. So they pull air in from the bottom on one side, blow it through the alternator, across the heads and then out over the mufflers.

So it's important that you don't run your Onan with much of a load or for a long time with the door (maintenance access cover) off it. With the door off most of the air comes out the front and doesn't go over the heads.

Does the generac do something like this or is it like the older Onan's where it relies on a more passive cooling? If it's passive I wonder if some permanently installed ventilation fans would help. Might be a fun and useful mod. Maybe an electric radiator fan could be installed with a thermostatic switch? Or some 110v muffin fans in the right places?

I've included a couple pictures below to show how the Onan works. Since it's much easier to see with pictures than with words.

During same hot spell, I went off the grid due to low voltage, and went on the generac genset 6.5KW. I noticed the voltage was high, I plugged in my RMS meter and was shocked to see 132Volts. I turned on the 15000BTU A/C and it came down to 128 and then I turned on the 13500BTU it then dripped to 124.
My question is; What should the zero load voltage be?
How can I adjust it to something lower if need be?

I appreciate all of the information that is made available on this forum, I find it to be a great resource.

Not directly related to this thread but an interesting note: The Onan generators use positive ventilation from a fan mounted in a fan shroud under the engine. So they pull air in from the bottom on one side, blow it through the alternator, across the heads and then out over the mufflers.

So it's important that you don't run your Onan with much of a load or for a long time with the door (maintenance access cover) off it. With the door off most of the air comes out the front and doesn't go over the heads.

Does the generac do something like this or is it like the older Onan's where it relies on a more passive cooling? If it's passive I wonder if some permanently installed ventilation fans would help. Might be a fun and useful mod. Maybe an electric radiator fan could be installed with a thermostatic switch? Or some 110v muffin fans in the right places?

I've included a couple pictures below to show how the Onan works. Since it's much easier to see with pictures than with words.

Generac is the same thing. It's a positive ventalation system. My only overheats happened while on the road so you can't really have the door open The heat coming off the pavemet and the exhaust from the v10 exiting in front of it doesnt help.